A study of the immunological properties of phage strains derived from T2 x T6 crosses revealed that the majority of the progeny differ serologically from the parental viruses. Some hybrids were found to contain head membranes having the serological specificity of both T2 and T6 phages, while others contained tail sheaths of the former and the tail fibers of the latter. Since the immunological properties of all hybrids were heritable, it has been concluded that the serological specificity of the head proteins of T2 and T6 is controlled by at least two genetic determinants, and that the specificities of the fiber and sheath proteins may be governed by single genes.
Furthermore it was found that nucleic acids of hybrids had similar proportions of unsubstituted, mono- and diglucosylated hydroxymethylcytosine nucleotides to the nucleic acid of either T2 or T6 phage. Since the parental and hybrid viruses having chemically similar nucleic acids contained in some instances serologically different proteins, it has also been concluded that the extent of glucosylation of the hydroxymethylcytosine component of viral nucleic acids and the immunological properties of viral proteins are independently heritable traits of T2 and T6 bacteriophages.